Series Crossovers for ALTEC

[LowOhms]

Question,

Has anyone besides Dominique Tanguy of Colonge used Series crossovers, rather than the usual Parallel crossovers, on ALTEC VOTTs or 604s? ( Dominique changed his A5 from Hiraga to Series ). Loved the change.

ALTEC themselves made a Series crossover for the 604E, the crossover known as the N1500A.

Many tube amp users report liking Series crossovers. I'm a tube amp user.

Presently, I know of only one person with a A7 in Canada who converted ( in early 2013 ) from Parallel to Series, a guitar player. He loved Series from the first note it played.

The late Irving M. "Bud" Fried ( Harvard attorney, USA importer of QUAD ESLs, DECCA and Lowther ) wrote two papers on Series crossovers, available on line. He relates, that the audio designers from Denmark (three decades ago) seem to have championed Series as sounding better. Fried also did audio shows in the USA with speaker crossovers where visitors could choose one or the other, Series or Parallel.

Surely, there are more than two people I've mentioned in the ALTEC universe using Series. Would like to hear their thinking and comments based on direct experience, or anyone else's, so we can all learn something.

I am just an ALTEC and speaker novice. I presently own pairs of 515Bs and 802-8Ds and 511s. Looking to build my first A7 system in early 2014. Thanks a lot..

Happy and Healthy New Year.

Jeff Medwin

[Old Guy]

There are NO magic solutions. Different approaches bring different problems. I played with series crossovers years ago. IMHO the response wasn't as flat. I say the best solution is active. Others may not agree.

There is so little data that you will likely have to produce your own, and it won't be valid for anyone else, as there are so many possibilities.

If, for instance, a combination of box and speakers is not flat, sometimes a deviation in the crossover can actually help. Unfortunately the researcher usually champions his data for all users, which it doesn't fit.

It's a system. Select components, tune the box, do the crossover last.

[LowOhms]

There are NO magic solutions. Different approaches bring different problems. I played with series crossovers years ago. IMHO the response wasn't as flat. I say the best solution is active. Others may not agree.

There is so little data that you will likely have to produce your own, and it won't be valid for anyone else, as there are so many possibilities.

If, for instance, a combination of box and speakers is not flat, sometimes a deviation in the crossover can actually help. Unfortunately the researcher usually champions his data for all users, which it doesn't fit.

It's a system. Select components, tune the box, do the crossover last.

Thanks OG for responding. It is interesting to see what ALTEC users with direct experience, such as you, say about this.

Happy, Healthy New Year.

Jeff Medwin

[bowtie427ss]

It is a very fine line that divides believing what you hear from hearing what you believe.

[LowOhms]

It is a very fine line that divides believing what you hear from hearing what you believe.

Well said. It requires that you be totally honest with yourself. I liked your comment a whole lot sir !!

Jeff Medwin

[Alien_Shore]

I did some fairly extensive research on the N1500a when I was playing around with a 604E last year.
The series crossover sounds excellent on my 604E, and it sims well:


in fact, i was hard-pressed to get any parallel design to simulate as well as the N1500a. The low part count, and great sound makes it a strong contender for the duplex. I suppose you could design one for an A7 application. Put it in PCD and do some sims, I'd be interested to see what you come up with!

[LowOhms]

I did some fairly extensive research on the N1500a when I was playing around with a 604E last year.
The series crossover sounds excellent on my 604E, and it sims well:


in fact, i was hard-pressed to get any parallel design to simulate as well as the N1500a. The low part count, and great sound makes it a strong contender for the duplex. I suppose you could design one for an A7 application. Put it in PCD and do some sims, I'd be interested to see what you come up with!

Thank you so much for sharing your interesting ( to me ) Series experience of a year ago. The N1500A by ALTEC is the simplest, first order Series, .... no wonder you like it!! Dominique Tanguy's Series A7, ( which easily up-ended his Hiraga ), is second order Series.

My interest is for a hi fi application, small room / close listening. I use low powered tube amps, and I intuitively lean towards use of first order ( 6 dB / octave ) filters. "Its KISS, minimalist messing with the signal approach."

A Forum Member from Canada, as I mentioned in the original post, ( who had "by ear" tweaked over time his A7 into a first order crossover alignment ), really loved it when he went from Parallel to Series in Q1 2013.

I will be loading my A7s with 515Bs, original cones, and I intend to initially employ "direct drive" from the amplifier to the 515B woofers. Second experiment on 515Bs is a first order high quality inductor of around 2 mHY, and determine by ear which I prefer, direct drive or inductor.

In Q1 2014 I am planning on having GPA install new 16 Ohm diaphragms on my 802s, and remagnetize them. Have 511B horns, will damp and modify them. Just need to "very soon" find A7 cabinets in Kansas City and brace and damp them as some of you have so kindly shown up here.

So far, from all I read here, I decided to double-up on the wood thickness inside the bottom of the ( inverted ) cabinet, and start my A7 / 515B listening with a 75 square inch full-width port - closest to the floor. I seek to couple the 515B's reflex bass energy to the listening room, because I use low powered tube amps and have a small room.

A word to all, I am mightily impressed with the ALTEC 515B woofer with original cone. It plays with a precision, and a dynamic contrast capability, and the ability to "project" that amazes me and it puts a smile on my face. I don't know of any other driver that does that !! It seems so low in distortion !

Now, I should relate, I have "cleaned" one of my pairs outer surrounds, as was discussed in Per Hasling's ALTEC article, and my initial impression, without TOTALLY verifying it ( by cleaning the second driver's outer surround and A-Bing them ) - is this is "mandatory" to do.

The clean surround driver sounds MUCH better in so many hard-to-describe ways, that it makes me want to suggest the procedure to ALTEC enthusiasts. No, I didn't mail my drivers back to Per in Denmark, I did them at home, took me about two days to do one driver. I bet 90% of the old ALTEC 15 inch drivers are out of spec, if using the original cone. These listening improvements I can now easily hear between my two drivers ( stock and cleaned outer surround) , and I am guessing, these improvements can not be obtained any other way ( E-Qing, etc. ) . Highly recommended. I am flabbergasted thus far. FYI, please review this :

http://www.haslingaudio.com/Altecsur...ory/story.html

http://www.haslingaudio.com/download...ofSurround.pdf


Comments and criticisms of my post are always welcomed. We all learn that way.



Jeff Medwin

[mah]

FYI, an article by Rod Elliot: Series vs. Parallel Crossover Networks

[LowOhms]

Thanks Mah,

I was totally familiar with that article, and I think that is a pretty funny. He tries to prove there is no difference between the two. Ha ! The way I read him, simply reading between the lines, with 6 dB slopes, he alludes Series is probably better.

It was all written "in Theory", like someone tying to "prove" there is no difference between wire for audio use, and wire is all just hype ( not!! ).

Perhaps a better read on the subject is BOTH of the white papers on the WWW by Irving M. "Bud" Fried. He was a great believer and user in first order crossovers, and in Series connections, and in 49 pages of his writings, he tells us "why". He suggests we need to learn from the past or continue making mistakes. There is much truth to that.

Perhaps best, certainly better than ANY theoretical answer, is to just listen to Series versus Parallel, and 6 dB versus 12 dB, with ALTEC drivers, as some people have done, and we can decide for ourselves. I intend to do this in 2014 on my own. I was just querying long time experienced ALTEC users in advance here on the subject. GM has referenced several times on this Forum to HIFI use of ALTEC A7s with minimalist crossovers " in the old days ".

Best wishes,

Jeff

[cradeldorf]

Jeff Markwart also found the N1500 a hard crossover to beat.
Kiss is my mantra too. Less is definitely more.